This proposal is for supplemental funds to my current grant (GM-23694) to investigate the thermoregulatory adjustments and metabolic changes during the electrophysiological states of sleep in humans exposed to different ambient temperatures. Specific studies will be conducted to determine: (a) changes in metabolism, vasomotor tone, and skin and core temperatures during stages of sleep at a thermoneutral temperature of 29 degrees; and (b) how stages of sleep, thermoregulatory mechanisms and metabolism are influenced by ambient temperatures above and below thermoneutrality (37 degrees, 34 degrees and 21 degrees, 24 degrees, respectively). These studies represent a collaborative research project planned by Dr. Craig Heller at Stanford University and myself at UC Santa Cruz. We believe that they should yield new insights into the interrelations between sleep, torpor, hibernation and thermoregulation and about the evolution and biological functions of sleep.